In many manufacturing operations, and particularly in the manufacture of cylindrical containers such as two-piece ferrous or aluminum cans, it is necessary to mass transport such articles, either in single file or en masse. Such containers are characteristically quite unstable, particularly at present-day line speeds which are capable of handling up to approximately 2500 articles per minute.
It is oftentimes necessary in multi-level installations to provide for means of elevating cylindrical or other objects during the processing operation. In view of the fact that when empty, articles such as cans tend to be marginally unstable and easily toppled if not handled with care, mass transport which would include can elevation is difficult to carry out, particularly at high line speeds.
Prior art elevators have characteristically employed either positive air pressure or vacuum-enhanced movable belting. Individually, each approach suffers from certain deficiencies. Although the use of positive air pressure angularly directed toward a rolling cylindrical article is capable of elevating said article rapidly and efficiently, lack of control of the speeding article at the elevator exit can result in damage to the elevated article as well as in a "log jam" as the various articles speed toward the point of transition between the elevator and the next downstream conveyor section.
Vacuum-enhanced movable belts are also not without their drawbacks. When a flexible porous belt is employed over a vacuum or low pressure, excessive belt wear often occurs. Belt failure requires the complete shutdown of the elevator assembly which could cause a complete plant closure and resulting economic loss.
An initial attempt was made to combine air actuation with vacuum belting in order to derive the benefits of each while eliminating their shortcomings. It was believed that by employing air actuation during the early stages of the elevator in order to build transport speed and vacuum-enhanced belting proximate the elevator exit to enhance article control, an improved elevator could be fabricated. As an enhanced benefit, belt wear would be greatly reduced for the belt path could be substantially shortened as the belt would only be required to encompass the vacuum section of the device and not the entire elevator area.
When initial attempts were made to fabricate a composite elevator, it was found that unanticipated problems arose at the transition point between the two elevator sections. Basically, the articles, such as rolling cans, travelling at high rates of speed within the lower or air-actuated section, would resist seating upon the vacuum-enhanced moving belt and would thus tend to fly off the elevator at the point of transition.
It is thus an object of the present invention to provide a single elevator having both air actuated and vacuum-enhanced belting sections which can be employed to gain the benefit of both approaches to article elevation, even at can speeds of 2500 cans per minute or higher.
It is yet a further object of the present invention to provide a composite elevator whereby an article, such as a rolling two-piece can, will progress from a first air-actuated section at a high rate of speed and will be caused to firmly and positively seat upon a vacuum-enhanced moving belt and remain upon the moving belt until discharge from the elevator has been completed.